The present invention relates to air conditioning systems for vehicles and more particularly to such systems wherein the interior of the systems is placed in communication with the atmosphere when the system is idle to militate against the formation and growth of microbial organisms, such as bacteria.
In existing air conditioning systems for vehicles, water tends to accumulate in the housing in which the evaporator is located. After a period of time, microbial growth tends to form, resulting in the source of objectionable odor. It has been discovered that the microbial growth is accelerated when air flow past the evaporator is greatly reduced or eliminated. The above condition tends to occur when the vehicle has been parked and the ignition is turned off. When the ignition is off, air conditioning (HVAC) systems with vacuum-type actuators will typically return or default to the same state that the system was in while the ignition was on. In the default condition, the door providing for re-circulation of interior air and prohibiting the admission of outside air will remain in the same state as it was when the ignition was on. If it remains in the recirculation state, air flow past the evaporated core is greatly reduced or eliminated during the period the vehicle is parked. It is at this stage that the microbial growth commences. The next time the ignition is turned on and the associated HVAC blower is caused to be energized, a severe odor is promptly detected.
Accordingly, it is desirable to open the interior of the HVAC housing to the outside air to improve interior air circulation and ventilation and greatly reduce microbial growth and the resultant objectionable odor.
It is an object of the invention to produce an HVAC system for a vehicle wherein the housing for the system will be automatically exposed to outside air after the ignition is turned off.
Another object of the invention is to produce an HVAC system for a vehicle wherein the cabin pressure and vacuum tend to be relieved to thereby facilitate the opening and closing of the vehicle doors.
The above as well as the objects and advantages of the invention may be achieved in an air conditioning system including a heat exchanger and a blower for moving air through the heat exchanger comprising a conduit providing communication between the atmosphere and the heat exchanger; a normally open valve in the conduit; a vacuum operated motor coupled to the valve; a source of vacuum; and a switch to selectively provide communication between said motor and said source of vacuum to effect movement of the valve to prevent communication between the atmosphere and the evaporator through the first conduit.